1. Field of the Invention
The present invention relates to a delivery pipe for use in an internal combustion engine that supplies fuel to the combustion chamber of each cylinder and injects fuel directly into the combustion chamber.
2. Description of Related Art
An in-cylinder fuel injection internal combustion engine in which fuel is injected directly into the combustion chamber of each cylinder is well known in diesel engines. Adoption of in-cylinder fuel injection in gasoline engines has also been proposed for the purpose of improving responsiveness of the engine, and the like.
In a typical in-cylinder fuel injection internal combustion engine, fuel from a fuel tank is pressurized by a high-pressure pump. After high-pressure fuel pressurized by the pump is supplied to a delivery pipe, high-pressure fuel is injected directly into the combustion chamber of each cylinder, from a corresponding one of injectors connected to the delivery pipe.
Among delivery pipes used in in-cylinder fuel injection internal combustion engines, a delivery pipe provided with a mounting portion for mounting the delivery pipe to the cylinder head of an internal combustion engine is described in, for example, Japanese Patent Application Laid-Open No. HEI 8-312502. The delivery pipe described in this laid-open patent application is shown in FIG. 5. A delivery pipe 202 has injector-inserting portions 200 for mounting injectors (not shown). A mounting portion 204 is formed near and corresponding to each injector-inserting portion 200.
The mounting portions 204 are for mounting the delivery pipe 202 near the mounting portion 204 to a cylinder head (not shown). Injectors are mounted to the injector-inserting portions 200, via O-rings (not shown).
In the delivery pipe 202 as described in Japanese Patent Application Laid-Open No. HEI 8-312502, the delivery pipe 202 is fastened to a cylinder head by screwing bolts into the cylinder head through screw holes 204a extending through the individual mounting portions 204 in a direction parallel to a plane perpendicular to an axis C of the delivery pipe 202.
The delivery pipe 2 has opposite end portions, 206 and 208. One end portion 206 is provided with a fuel inlet opening (not shown) and an outlet opening (not shown), and the other end portion 208 is provided with a closed internal fuel space (not shown). None of the mounting portions 204 is disposed at either one of the opposite end portions 206 and 208.
In the delivery pipe 202, therefore, opposite end lengths outward of the outermost mounting portions 204 (that is, end lengths extending outward of lines D1 and D2 as indicated by arrows in FIG. 5) cannot readily be restrained. In some cases, the end lengths of the delivery pipe 202, extending outward of the outermost mounting portions 204, deform due to high-pressure fuel supplied into the delivery pipe 202. The end lengths of the delivery pipe 202 outward of the mounting portions 204 may also deform due to various thermal contractions within the delivery pipe 202 caused by ambient temperature changes, particularly at very low temperature ranges.
Since the mounting portions 204 and the injector-inserting portions 200 cannot be provided at exactly the same positions, it is impossible or very difficult to completely restrain the delivery pipe end lengths extending outward of the mounting portions 204, as indicated in FIG. 5, in order to prevent deformation of the end lengths of the delivery pipe 202. Therefore, an injector connected to one of the end lengths of the delivery pipe 202 (an injector connected to the injector-inserting portion 200 at the extreme left in FIG. 5) may suffer a loosening of its junction with the delivery pipe 202, thereby causing deterioration of the fuel sealing.